Heated transfer vessel for molten metal casting apparatus and method



May 26, 1970 E G SCHEMPP ETAL HEATED TRANSFER VESSEL FOR MOLTEN METALCASTING APPARATUS AND METHOD 2 Sheets-Shee'z 2 Filed Feb. 8, 1968 E mm0. W G %M sa BO y E TTORA EY United States Patent O 3,514,519 HEATEDTRANSFER VESSEL FOR MOLTEN METAL CASTING APPARATUS AND METHOD EberhardG. Schempp, Glenshaw, and Robert J. Taylo',

McKees Rocks, Pa., assignors to Lectromelt Corporation, Pittsburgh, Pa.,a corporation of Delaware Filed Feb. 8, 1968, Ser. No. 703.942 Int. Cl.Hb 3/62; B22d 11/00 U.S. Cl. 13--20 12 Claims ABSTRACT OF THE DISCLOSUREA refractory lined molten metal transfer vessel having at least oneupper inlet for receiving molten metal from a ladle and at least onelower nozzle for discharging molten metal into a continuous castingapparatus. Resistance heating means Supplies radiant energy to thevessel and the molten metal, and an inlet for inert gas is provided tominimize oxidation of the molten metal and the resistance heating means.

BACKGROUND OF THE INVENTION tundish. The transfer vessel has one or morenozzles at its lower end for discharging molten metal into one or moregenerally vertically arranged molds having an upper opening and meansfor continuously withdrawing the ingot from its lower end.

The various handling procedures, which occur before the molten metal iscast, include tapping of the furnace, discharging of the metal into aladle, possible additional metallurgical treatments such as vacuumdegassing, transporting the ladle to the casting apparatus, discharge ofthe metal into the transfer vessel and, finally, the discharge of themetal into the molds. This time lapse between tapping and teeming mayresult in substantial heat loss in the molten metal. Also, vari-ableconditions of the ladle, of the tap, of the transfer, of the slagblanket and added processes, result in a wide range of actualtemperature losses from heat to heat. In order to insure that such heatlosses do not lower the melt temperature below that necessary forsuccessful casting, excessive furnace tapping temperatures wereheretofore required.

A serious chilling effect may also occur as molten metal is dischargedfrom a ladle into a relatively cold transfer vessel. This isparticularly serious since the first portion of molten met-al to enterthe tundish is generally at a substantially lower temperature than thebulk of the ladle content. For example, in a ISO-ton ladle thetemperature difference 'between the top and bottom layers of moltenmetal may be as much as 40 F.

In addition, oxidation may occur in the stream of molten metal fallinginto the transfer vessel frorn the ladle as well as to the surface ofthe molten metal as it flows to the various discharge nozzles. Thiscontaminates the metal with hydrogen, oxygen and nonmetallic inclusionsand, in addition, seriously shortens the life of the refractory and thetransfer vessel.

It is an object of the invention to provide a new irnproved transfervessel for a continuous casting apparatus.

Another object of the invention is to provide a con- "ice tinuouscasting transfer vessel having means for regulating the melt temperatureduring -a casting operation.

A further object of the invention is to provide means to prevent thechilling of molten metal in a transfer vessel during a continuouscasting operation.

Yet another object of the invention is to provide means to preventoxidation of molten metal in a transfer vessel during a continuouscasting operation.

These and other objects and advantages of the instant invention willbecome more apparent from the description of the preferred embodimenttaken with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational Viewillustrating a continuous casting apparatus incorporating the instantinvention;

FIG. 2 is a side elevational view, partly in section, of the transfervessel according to the instant invention;

FIG. 3 is a top plan View of the transfer vessel illustrated in FIG. 2;

FIG. 4 is a fragmentary view of the heating rod assernbly of thetransfer vessel illustrated in FIG. 2; and

FIG. 5 is a fragmentary View illustrating the heating elements clarnpsuseable with the transfer vessel according to the invention.

SUMMARY OF THE INVENTION A refractory lined molten metal transfer vesselhaving at least one molten metal inlet and at least one molten metaloutlet and means for heating the molten metal and vessel during acontinuous casting operation. The invention may also include means forproviding an inert gas atmosphere within the vessel.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 ingreater detail, the transfer vessel or tundish 10 is shown to bedisposed between a ladle 11 and the mold 12 of the continuous castingapparatus. The ladle 11 is provided with a spout 14 that is normallyclosed `by a plug (not shown) which may be operated frorn a remotelocation by means which are not shown but which are well known in theart The tundish 10 may be generally pear-shaped in vertical section andinclude a body portion 16 and a cover portion 17. An inlet pipe 18 opensinto the cover portion 17 and is disposed in registry with the ladlespout 14, and one or more discharge nozzles or ports 20 open into thelower end of the tundish body 16. Disposed below each of the dischargenozzles 20 and in general registry therewith is the mold 12 of thecontinuous casting operation. The continuous casting apparatus forms nopart of the instant apparatus and, accordingly, Will not be discussed indetail. For purposes of understanding the instant invention, it will besuffcient to state that the mold 12 includes an inlet 21 at it s upperend and means 23 at its lower end for continuously withdrawing the ingot24.

Referring now to FIGS. 2 and 3, the tundish body 16 is shown to comprisean elongate trough-like body having side walls 28 'which slope gentlyupwardly from its lower end and comprising an outer metallic shell 29and an inner refractory lining 31 which may be composed, for example, ofMgO or MgO-Cr O mixture. The discharge nozzles 20 are preferablydisposed in equispaced relation along the lower end of the tundish body,and each is composed of a zirconia cast refractory which is illustratedas a single member but which may be composed of a plurality of shapemembers as well.

The cover 17 is substantially coextensive with the tundish body 16comprises a metallic frame 33 for supporting a generally vertical sidewall portion 34 and an arched roof 35, each of which is composed of ahigh alumina cast refractory material. A generally tubular inlet nozzle37, formed of cast high alumina refractory, extends vertically throughan opening 38 formed generally in the center of the arched roof 35 andextends downwardly to the lower edge of the cover 17.

A plurality of equally spaced apart heating assemblies 40 extendtransversely across the cover 17 for preheating the tundish and formaintaining or elevating the melt temperature during a castingoperation. The heating assemblies 40 are each received through one of aplurality of pairs of aligned openings 42 which are formed transverselyin the side wall portion 34 of cover 17 wherein the heating assemblies40 are supported in a generally parallel relation below the arched roof35.

Each heating assembly 40 may comprise a heating rod 43 extendingtransversely across the cover 17 beneath the arched roof 35 and which isheld in position by a pair of elongate, generally cylindrcal holders 45which are disposed in general alignment within the apertures 42 andextend outwardly therefrom for engagement by clamp assemblies 46. Asseen in FIG. 4, the rod 43 and the holders 45 may each be composed ofgraphite and may be joined in any suitable manner such as by anexternally threaded graphite nipple member 48 which is received inthreaded openings 50 and :51 suitably formed in the ends of the heatingrods 43 and the holders 45, respectively.

As seen particularly in FIG. 5, the clamps 46 have a pair of opposedgenerally arcuate shoes 52 which are sutably held in high pressureengagement with their respective holders 45, and each clamp is suitablyconnected to bus bars 53 which are in turn connected to a source ofelectrical energy (not shown). The clamp shoes 52 and the bus bars 53may be composed of any suitable conductive material, such as Copper, andeach may be provided with means to permit the circulation of coolingfluid, such as the tubing 54 within the clamp shoes 52 and the hollowinterier of the bus bars 53. Those skilled in` the art -will appreciatethat the bus bars 53 will be connected to a suitable energy source. I

The roof 35 may also have one or more apertures 50 which may be providedwith a nipple 56 for receiving a Conduit 57 whose other end may beconnected to a suitable source of inert gas, such as nitrogen.

In operation, the heating elements 43 -will be energized prior to thebeginning of a casting operation to preheat the inner surface of therefractory lining 31 to' approximately the temperature of the liquidmetal to be cast. This prevents chilling of the steel as it is beingdischarged from the ladle into the tundish through the inlet nozzle 37.The heating assemblies 40 may also remain energized during the castingoperation so that the temperature of the molten steel may be maintainedat a desired level or even elevated. This insures satisfactory castingand pre- 'vents freezing of the molten metal within the dischargenozzles 20.

Those skilled in the art will appreciate that the molten metal enteringthe tundish will flow to each end of the tundish body 16 and dischargethrough each of the nozzles into a mold of the continuous castingapparatus disposed therebelo'w. In addition, a final temperatureadjustment may be made during the casting operation so that the 'steeltemperature may be maintained within the relatively narrow range neededfor successful continuous casting, regardless of variations in theladle, the tap, the transfer, the slag blanket at any intermediatemetallurgical processes. In addition, the nonreducing nitrogenatmosphere within the tundish cover avoids oxidation of the streamfalling into :the tundish and of the surface of the steel fiowing towardthe nozzles. This not only prolongs refractory life, but avoidscontamination of the steel by hydrogen, oxygen and nonmetallicinclusions.

While only a single 'type of heating assembly has been disclosed, thisis intended to be merely illustrative, since those skilled in the artwill appreciate that other types of heating assemblies may also beemployed. In addition, while only a single embodiment of the instantinvention has been shown and described, it is not intended to be limitedthereby, but only by the scope of the appended claims.

We claim:

1. A vessel for transfer-ing molten metal from a ladle to continuouscasting apparatus, said vessel comprising a hollow body portion havingan open upper end and a cover portion substantially coextensive withsaid body portion, said body portion having at least one port fordischarging molten metal to said casting apparatus, said cover having atleast one port for receiving molten metal from said ladle and radiantelectrical heating means supported beneath said cover for preheatingsaid body portion and controlling the temperature of molten metaltherein.

2. The vessel set forth in claim 1 wherein gas inlet means is providedin said cover so that an inert gas atmosphere may be introduced intosaid vessel.

3. The vessel set forth in claim 1 wherein said body portion is elongateand has a plurality of spaced discharge nozzles opening into its lowerend.

4. The vessel set forth in claim 1 wherein said radiant heating meanscomprises electrical resistance heating elements. 4

5. The vessel set forth in claim 1 wherein said cover is composed of arefractory thermal insulating material and is generally arched.

6. The vessel set forth in claim 1 wherein said radiant heating meanscomprises at least one graphite heating element extending through anopening in said cover, and clamping means for supporting said graphiteheating element and for connecting the same to a source of electricalenergy.

7. The vessel set forth in claim 6 wherein gas inlet means is providedin said cover so that an inert gas atmosphere may be introduced intosaid vessel.

8. The vessel set forth in claim 7 wherein said body portion is elongateand has a plurality of spaced discharge nozzles opening into the lowerend thereof.

9. The vessel set forth in claim 8 wherein said cover is composed of arefractory thermal insulating material and is generally arched torefiect radiant heat to said body portion.

10. The vessel set forth in claim 9 wherein the port in said cover islocated generally at the center thereof and wherein said discharge portsare arranged vertically in substantial alignment and spaced from saidentrance port, and wherein said radiant heating means comprises aplurality of graphite rod means spaced along said cover to,

substantially uniformly heat said body portion, said entrance portcomprising a nozzle extending downwardly from said cover toward saidbody portion.

1 1. -In the method of continuously casting molten metal; the steps ofintroducng said metal from a ladle into a transfer vessel, heating saidmetal with graphite resistance heating means while in said transfervessel, and discharging said molten metal into continuous castingapparatus from a plurality of spaced apart discharge nozzles in saidtransfer vessel, introducng an atmosphere of inert gas into said vessel.

12. The method set forth in claim 11 and including the step ofpreheating said vessel prior to the introduction of molten metal theretofrom said ladle.

References Cited UNITED STATES PATENTS 2,27l,838 2/1942 Hanawalt 13-202,682,566 6/1954 Wahlberg 13--20 X 3,273,208 9/ 1966 Greenberger i164--281 H. B. GILSON, Primary Examiner U.S. CI. X.R. 164-281

